+1
With the notable exception that car values depreciate quickly; that's not necessarily the case with musical instruments. But my point is pretty irrelevant to the topic anyway.
----------
Look, it's up to the individual musician. People hear a guy play very well (and look older than a teenager) and think, "wow! he/she's good and it looks like he/she's been playing that thing forever!"
--or--
They hear a rookie playing poorly and think, "Poor dude couldn't even afford a decent instrument. Look! It's already been used all to hell by the last guy who owned it. Must be a craiglist special."
--or--
They hear a teenager playing and see him with a "relic" and think, "Looks like his Uncle Earl passed down the ol' family bass for the kid to learn on. Well, if he sticks with it, he'll get better (or 'he sounds pretty good on that old thing')."
In any case, does it really matter?
If you want to look like you don't take care of your gear and that's cool to you...so be it!
If you want to relic your stuff, relic it! Just don't expect to be able to sell it later for much (unless you're famous). If that's cool with you--go for it!